Patent application DE 31 31 138 A1 of the applicant describes a load-shiftable planetary gear change-speed transmission with several coupled planetary gear sets. Therein, a staged planetary gear set is used, on the carrier of which planetary gears with different effective diameters are arranged. In the embodiment according to FIG. 11, an inner central gear meshes with the larger effective diameter of the planetary gears, and two outer central gears mesh with each of the two effective diameters of the planetary gears of the staged planetary gear set. Thus, the staged planetary gear set features a total of four shafts in the order of rotational speeds. Subsequently, one of the two outer central gears is connected to an inner central gear of a second planetary gear set formed as a positive gear set.
Patent application DE 10 2008 041 192 A1 of the applicant describes a multi-speed transmission, whereas a first and fourth planetary gear set are arranged in a common gear set plane. Thereby, the ring gear of the fourth planetary gear is firmly connected to a sun gear of the first planetary gear set. The two carriers of the first and fourth planetary gear sets are likewise firmly connected to each other. Thus, the first and fourth planetary gear sets together feature a total of four shafts in the order of rotational speeds.
Moreover, in the state of the art, a multitude of vehicle transmissions are known, with which the formation of gears takes place through fixed rotational speed relationships of the shafts of the planetary gear set system that is coupled multiple times, which feature one order of rotational speeds with each other. As an example, U.S. Pat. No. 5,106,352 A is known, with which two different sized rotational speed paths are transmitted to a planetary gear set that is coupled twice, which features four shafts in the order of rotational speeds.
A system with a total of five shafts in the order of rotational speeds already offers a high degree of freedom for the formation of gears. The five shafts are characterized in that the rotational speeds of such shafts increase, decrease or remain the same in a linear fashion in the specified sequence. In other words, the rotational speed of the first shaft is less than or equal to the rotational speed of the second shaft. In turn, the rotational speed of the second shaft is less than or equal to the rotational speed of the third shaft. The rotational speed of the third shaft is less than or equal to the rotational speed of the fourth shaft. The rotational speed of the fourth shaft is less than or equal to the rotational speed of the fifth shaft. This sequence is also reversible, such that the fifth shaft features the lowest rotational speed, while the first shaft assumes a rotational speed that is greater than or equal to the rotational speed of the fifth shaft. Thereby, there is always a linear relationship between the rotational speeds of all five shafts. Thereby, the rotational speed of one or more of the five shafts may also assume negative values, or even the value of zero. Therefore, the order of rotational speeds is always to refer to the signed value of the rotational speeds, and not to their amount.
If the rotational speed of two of the five shafts is given as fixed, the rotational speeds of the remaining three shafts are specified. A planetary gear set system with five shafts is in the order of rotational speeds, but can only be achieved through the coupling of at least three individual planetary gear sets. This requires a significant structural complexity, and increases the size of the transmission compared to a planetary gear set system with only four shafts in the order of rotational speeds.
The change-gear transmission according to FIG. 1 of the patent DE 38 18 710 C1 actually includes six shafts in the order of rotational speeds. For this purpose, a total of two sun gears and two ring gears are allocated to dual planetary gears of a planetary gear set. A sun gear of an additional individual planetary gear set formed as a negative gear set is firmly connected to each sun gear, which meshes with the smaller diameter of the dual planetary gears. The carrier on which the dual planetary gears are rotatably mounted is firmly connected to the carrier of the additional individual planetary gear set. The additional individual planetary gear set is arranged axially adjacent to the dual planetary gears, by which the axial structural length of the transmission is increased.
The axial structural length of a transmission is of great importance for use in the motor vehicle drive train. Particularly with vehicles with drive trains arranged transversely to the direction of travel of the motor vehicle, attention must be paid to a particularly short axial structural length, since, in the axial conjunction with the internal combustion engine and (if applicable) a start-up element, the transmission is arranged between the longitudinal beams of the front section of the motor vehicle. With hybrid vehicles, an electric motor is also added to this conjunction, by which the need for installation space of the drive train is further increased.